What is the most carbon-efficient external wall retrofit approach for a typical Irish semi-detached house?
Life Cycle Analysis
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Timothy O' Leary
EPS insulation emits 11kg more embodied carbon than wood fibre insulation across all life cycle stages. However, rock mineral wool is only 4kg more carbon-intensive than wood fibre insulation.
The increased concentration of anthropogenic greenhouse gas emissions in the atmosphere reduces the ability of long-wave heat to escape from the earth. The concentration of carbon dioxide (CO2) contributes the greatest to global warming due to its abundance and ability to remain in the atmosphere for thousands of years. 1
The building sector accounts for 39% of global CO2 emissions. Ireland's contribution primarily arises from the residential dwellings as they emit almost 60% more CO2 than an average European home2 . Therefore, the government of Ireland strives to retrofit 500,000 houses by 2030 to improve energy efficiency and minimise carbon emissions of the existing building stock. However, the embodied carbon associated with the materials implemented during a retrofit may rise significantly and exceed the lifetime energy savings3. Therefore, this study addresses the embodied carbon content of insulation products as part of an external wall retrofit.
Life Cycle Analysis (LCA) was employed to evaluate the carbon intensity of several biogenic, synthetic and mineral insulation products obtained from an Environmental Product Declaration (EPD) database. The scope of this life cycle assessment was from Cradle-to-Grave or from raw material extraction to the end of life. The production stage (Modules A1-A3) is highly carbon-intensive and was primarily assessed. By referring to the environmental impact categories declared within an EPD, materials contribution to Global Warming Potential (GWP) and other essential factors was established. In addition, a series of bar charts were created based on the results expressed in kilograms to facilitate visual comparison between insulation products to seek the least carbon-intensive. OneClickLCA was then incorporated to establish the total CO2e emitted over the Cradle-to-Grave life cycle stages.
In general, raw material extraction (A1) is the most impactful module of the Product Stage. Materials which naturally sequester carbon, such as wood fibre, must be implemented more. The study revealed that EPS insulation emits 11 kg more embodied carbon than wood fibre insulation across all life cycle stages. However, rock mineral wool is only 4 kg more carbon-intensive than wood fibre insulation.